I guess I haven't. I also don't write many tests, but I do write a testsuite when I get really stuck with something. For example, I couldn't trust my floating-p

I guess I haven't. I also don't write many tests, but I do write a testsuite when I get really stuck with something. For example, I couldn't trust my floating-point implementation in a RISC-V emulator, so I wrote a program that should run inside it that asserts on every operation and C-function that does floating-point calculations. I found so many bugs using that. But, I also don't particularly care, you know. If you're doing something as a hobby, don't sweat about the tests. Just do it because it's fun - and the second it stops being fun do something else.